Derivatives of 1H-triazolo[4,5-c]pyridine-7-carboxylic acids and esters

ABSTRACT

New derivatives of 1H-triazolo[4,5-c]pyridine-7-carboxylic acids and esters and their acid addition salts having the general formula ##SPC1## 
     Are disclosed. They are useful as anti-inflammatory agents and central nervous system depressants. In addition, this type of compound increases the intracellular concentration of adenosine-3&#39;,5&#39;-cyclic monophosphate.

This application is a division of application Ser. No. 471,537, filedMay 20, 1974, U.S. Pat. No. 3,929,812, Dec. 30, 1975.

SUMMARY OF THE INVENTION

This invention relates to the new derivatives of1H-triazolo[4,5-c]pyridine-7-carboxylic acids and esters, and acidaddition salts thereof, having the general formula ##SPC2##

The symbols have the following meaning in formula I and throughout thisspecification.

R is hydrogen or lower alkyl.

R₁ is hydrogen, lower alkyl, phenyl or phenyl-lower alkyl.

R₂ is lower alkoxy, or a basic nitrogen group ##EQU1## wherein R₄ ishydrogen, lower alkyl, di(lower alkyl)amino (lower alkyl) and R₅ ishydrogen, lower alkyl or phenyl. The basic group may also form asaturated heterocyclic of 5 or 6 members in which an additional nitrogenis present, i.e., pyrrolidino, piperidino, pyrazolyl, pyrimidino,pyridazinyl or piperazino, each of which may bear as a substituent ahydroxy-lower alkyl group or one or two lower alkyl groups especiallythe piperidine and piperazine heterocyclics. R₂ may also be a hydrazine##EQU2## or a hydrazone ##EQU3## wherein R₆, R₇ and R₈ each is hydrogen,lower alkyl or phenyl, and R₉ is lower alkyl or phenyl.

R₃ is hydrogen, lower alkyl or phenyl.

The lower alkyl groups referred to throughout this specification includestraight or branched chain hydrocarbon groups containing 1 to 7 carbonatoms, preferably 1 to 4 carbons. Examples of the type of groupscontemplated are methyl, ethyl, propyl, isopropyl, etc. The lower alkoxygroups include such lower alkyl groups bonded to an oxygen, e.g.,methoxy, ethoxy, propoxy, isopropoxy, etc. The phenyl-lower alkyl groupsinclude such lower alkyl groups bonded to a phenyl, e.g., benzyl,phenethyl, etc.

Preferred embodiments of this invention are as follows:

R is hydrogen or lower alkyl of 1 to 4 carbons, especially ethyl.

R₁ is hydrogen or lower alkyl of 1 to 4 carbons, especially ethyl orbutyl.

R₂ is lower alkoxy of 1 to 4 carbons, especially ethoxy, amino, loweralkylamino of 1 to 4 carbons, especially ethylamino or butylamino,##EQU4## wherein R₆ is hydrogen and R₇ is hydrogen or lower akyl of 1 to4 carbons, especially wherein both R₆ and R₇ are hydrogen, or ##EQU5##wherein R₈ and R₉ are both methyl. R₃ is hydrogen or lower alkyl of 1 to4 carbons, especially methyl.

DETAILED DESCRIPTION OF THE INVENTION

The new compounds of formula I are formed by the following series ofreactions.

A 4,6-dihydroxypyridine carboxylic acid ester of the formula ##SPC3##

[produced analogous to the procedure described in Chem. Ber. 99, 244,1966] is made to react with an inorganic acid chloride like phosphorusoxychloride, producing a compound of the formula ##SPC4##

with chlorine atoms in 4- and 6-positions of the molecule. This compoundis now treated in an organic solvent like alcohol with the appropriateamine of the formula

(IV)

     H.sub.2 N--R.sub.1

at about 80° C in the presence of a base, e.g., an alkylamine liketriethylamine. By this reaction a product of the formula ##SPC5##

is obtained.

This compound of formula V is made to react with an alkali metalalcoholate. By this procedure a compound of the formula ##SPC6##

is produced with an alkoxy group in the 6-position of the molecule. Thiscompound is now hydrogenated either catalytically or with a metal-acidpair such as zinc in acetic acid. This results in the formation of acompound of the formula ##SPC7##

Compounds of the formula ##SPC8##

wherein R₂ is alkoxy are now produced by reacting a compound of formulaVII with an alkali metal nitrite in an acid medium, e.g., sodium nitritein acetic acid. Compounds of the formula ##SPC9##

wherein R₂ is an amino group are produced by the reaction of a compoundof formula Ia with an amine of the formula ##EQU6## It is sometimesnecessary to utilize an autoclave for this reaction. Compounds of theformula ##SPC10##

wherein R₂ is a hydrazino group are obtained by the reaction of acompound of formula Ia with an appropriate hydrazine of the formula##EQU7## Compounds of the formula ##SPC11##

are produced by the reaction of a compound of formula Ic wherein R₆ andR₇ are both hydrogen, with an appropriate aldehyde or ketone of theformula ##EQU8##

Compounds of formula Ib, wherein R₄ and R₅ are not hydrogen arealternatively produced by the reaction of a compound of formula V withthe appropriate amine of the formula ##EQU9## producing a compound ofthe formula ##SPC12##

which is now processed as described above, i.e., hydrogenation andsubsequent reaction with the alkali metal nitrite in acid medium.

The free acid, wherein R is hydrogen, is obtained by hydrolysis of theester, e.g., by treatment with an aqueous base like sodium hydroxidesolution.

The bases of formula I form pharmaceutically acceptable acid additionsalts by reaction with equivalent amounts of the common inorganic andorganic acids. Such salts include the hydrohalides, e.g., hydrobromide,hydrochloride, sulfate, nitrate, phosphate, acetate, citrate, oxalate,tartrate, maleate, succinate, benzoate, ascorbate, alkanesulfonate,e.g., methanesulfonate, arylsulfonate, e.g., benzenesulfonate,toluenesulfonate, etc. It is frequently convenient to purify or isolatethe product by forming an insoluble salt. The base is obtained byneutralization and another salt then formed by treatment with theappropriate acid.

The new compounds of this invention have anti-inflammatory propertiesand are useful as anti-inflammatory agents, for example, to reduce localinflammatory conditions such as those of an edematous nature orresulting from proliferation of connective tissue in various mammalianspecies such as rats, dogs and the like when given orally in dosages ofabout 5 to 40 mg/kg/day, preferably 5 to 20 mg/kg/day, in single or 2 to4 divided doses, as indicated by the carageenan edema assay in rats. Theactive substance can be utilized in compositions such as tablets,capsules, solutions or suspensions containing up to about 300 mg. perunit of dosage of a compound or mixture of compounds of formula I orphysiologically acceptable acid addition salt thereof. They can becompounded in conventional manner with a physiologically acceptablevehicle or carrier, excipient, binder, preservative, stabilizer, flavor,etc. as called for by accepted pharmaceutical practice. Topicalpreparations containing about 0.01 to 3 percent by weight of activesubstance in a lotion, salve or cream may also be used.

The new compounds of this invention are central nervous systemdepressants and can be used as tranquilizers or ataractic agents for therelief of anxiety and tension states, for example, in mice, cats, rats,dogs and other mammalian species, in the same manner aschlordiazepoxide. For this purpose a compound or mixture of compounds offormula I, or non-toxic, physiologically acceptable acid addition saltthereof is administered orally or parenterally in a conventional dosageform such as tablet, capsule, injectable or the like. A single dose, orpreferably 2 to 4 divided daily doses, provided on a basis of about 1 to3 mg. per kilogram per day, preferably about 2 to 15 mg. per kilogramper day, is appropriate. These may be conventionally formulated in anoral or parenteral dosage form by compounding about 10 to 300 mg. perunit of dosage with conventional vehicle, excipient, binder,preservative, stabilizer, flavor or the like as called for by acceptedpharmaceutical practice.

The new compounds also increase the intracellular concentration ofadenosine-3',5'-cyclic monophosphate, and thus by the administration ofabout 1 to 50 mg/kg/day, preferably about 10 to 50 mg/kg, in single ortwo to four divided doses in conventional oral or parenteral dosageforms such as those described above may be used to alleviate thesymptoms of asthma.

The following examples are illustrative of the invention and constitutepreferred embodiments. Other members of the class are produced by theprocedures illustrated by appropriate substitution of the principalreactants. All temperatures are in degrees celsius.

EXAMPLE 14-Ethoxy-1-ethyl-6-methyl-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylicacid, ethyl ester

a. 4,6-Dichloro-2-methyl-5-nitropyridine-3-carboxylic acid ethyl ester

242 g. of 4,6-dihydroxy-2-methyl-5-nitropyridine-3-carboxylic acid ethylester (1 mol.) are heated at 120° with 500 ml. of phosphorus oxychloridefor 3 hours. After this time, the excess phosphorus oxychloride isremoved in vacuo and the black residue is decomposed by pouring intoice-water. About 1 liter of chloroform is added and the mixture isfiltered to remove undissolved material. The organic layer is separatedand the aqueous phase is extracted twice with 100 ml. portions ofchloroform. The extract is dried over calcium chloride, filtered andevaporated to dryness. The resulting oil is crystallized with about 500ml. benzene, yielding 153 g. of4,6-dichloro-2-methyl-5-nitropyridine-3-carboxylic acid ethyl ester(55%); m.p. 45°-46°.

b. 6-Chloro-4-ethylamino-2-methyl-5-nitropyridine-3-carboxylic acidethyl ester

27.9 g. of 4,6-dichloro-2-methyl-5-nitropyridine-3-carboxylic acid ethylester (0.1 mol.) are dissolved in 100 ml. of ethyl alcohol and 12 g. oftriethylamine. At reflux temperature a solution of 4.5 g. of ethylaminein 50 ml. of alcohol is slowly added dropwise with continual stirring.After the addition is completed, the reaction mixture is refluxed for anadditional 30 minutes. The solvent is then removed in vacuo and theresidue is dissolved in 300 ml. of petroleum ether. The triethylaminehydrochloride is filtered off and the filtrate cooled to 0°;6-chloro-4-ethylamino-2-methyl-5-nitropyridine-3-carboxylic acid ethylester crystallizes, yield: 69%, m.p. 36°-37° (methanol).

c. 4-Ethylamino-6-ethoxy-5-nitro-2-methylpyridine-3-carboxylic acidethyl ester

287 g. of 6-chloro-4-ethylamino-5-nitro-2-methylpyridine-3-carboxylicacid ethyl ester (1 mol.) are slowly added to a gently refluxing mixtureof 24 g. of sodium in 750 ml. of dry alcohol. The mixture is heated withstirring for an additional hour. After cooling to room temperature, thesodium chloride is filtered off and the filtrate evaporated to dryness.The oily residue of4-ethylamino-6-ethoxy-5-nitro-2-methylpyridine-3-carboxylic acid ethylester is crystallized with methanol, yield 305 g. (82%); m.p. 40°-42°.

d. 5-Amino-4-ethylamino-6-ethoxy-2-methylpyridine-3-carboxylic acidethyl ester

166 g. of 4-ethylamino-6-ethoxy-5-nitro-2-methylpyridine-3-carboxylicacid ethyl ester are dissolved in 500 ml. of butyl alcohol. 300 mg. ofpalladium on charcoal (10%) are added and the mixture is hydrogenated at80°. After the theoretical amount of hydrogen has been absorbed, thesolution is filtered and the solvent distilled off. Distillation of theremaining colorless oil yields 125 g. of5-amino-4-ethylamino-6-ethoxy-2-methylpyridine-3-carboxylic acid ethylester, b.p. 170-175/₀.05.

e.4-Ethoxy-1-ethyl-6-methyl-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylicacid ethyl ester

26.7 g. of 5-amino-4-ethylamino-6-ethoxy-2-methylpyridine-3-carboxylicacid ethyl ester (0.1 mol.) are dissolved in 100 ml. of acetic acid. Atroom temperature 7.5 g. of sodium nitrite in 20 ml. of water are addeddropwise with continual stirring. The temperature is kept below 20°. Themixture is stirred overnight and then evaporated to dryness. 100 ml. ofwater are added to the residue which is then extracted three times with50 ml. portions of ether. The organic layer is collected, dried oversodium sulfate, filtered and the solvent distilled off. The residue of4-ethoxy-1-ethyl-6-methyl-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylicacid ethyl ester is recrystallized from ligroin, yield 75%, m.p.56°-58°.

f.4-Ethoxy-1-ethyl-6-methyl-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylicacid

20 g. of4-ethoxy-1-ethyl-6-methyl-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylicacid ethyl ester are hydrolyzed with aqueous sodium hydroxide to obtain4-ethoxy-1-ethyl-6-methyl-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylicacid.

The following additional compounds are obtained by the foregoingprocedure:

1-Ethyl-4-methoxy-6-methyl-1H-1,2,3-triazolo[4,5-c]-pyridine-7-carboxylicacid methyl ester.

4-n-butoxy-1-methyl-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylic acidn-butyl ester.

1,6-diethyl-4-ethoxy-1H-1,2,3-triazolo[4,5-c]pyridine- 7-carboxylic acidand ethyl ester.

4-Pentoxy-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylic acid and ethylester.

4-Ethoxy-1-ethyl-6-phenyl-1H-1,2,3-triazolo[4,5-c]-pyridine-7-carboxylicacid ethyl ester.

4-Methoxy-1-phenyl-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylic acidmethyl ester.

4-Propoxy-6-methyl-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylic acidpropyl ester.

4-Ethoxy-1-ethyl-6-propyl-1H-1,2,3-triazolo[4,5-c]-pyridine-7-carboxylicacid ethyl ester.

1-Benzyl-4-methoxy-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylic acidmethyl ester.

4-Ethoxy-6-methyl-1-phenethyl-1H-1,2,3-triazolo-[4,5-c]pyridine-7-carboxylicacid ethyl ester.

4-Ethoxy-6-methyl-1-phenyl-1H-1,2,3-triazolo[4,5-c]-pyridine-7-carboxylicacid and methyl ester.

4-Ethoxy-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylic acid ethyl ester.

4-Ethoxy-1-phenethyl-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylic acidethyl ester.

EXAMPLE 24-Butylamino-1-ethyl-6-methyl-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylicacid ethyl ester

2.8 g. of4-ethoxy-1-ethyl-6-methyl-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylicacid ethyl ester is treated for 14 hours with 10 ml. of n-butylamine atreflux temperature. The excess butylamine is distilled off and theresidue of4-butylamino-1-ethyl-6-methyl-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylicacid ethyl ester is recrystallized from petroleum ether, yield 78%, m.p.85°-87°.

EXAMPLE 31-Ethyl-6-methyl-4-isopropylamino-1H-1,2,3-triazolo[4,5-c]-pyridine-7-carboxylicacid ethyl ester

By substituting isopropylamine for the n-butylamine in the procedure ofExample 2,1-ethyl-6-methyl-4-isopropyl-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylicacid ethyl ester is obtained, yield 83%, m.p. 55°-57° (petroleum ether).

The following additional compounds are obtained by the procedure ofExample 2 by substituting the appropriate amine for the butylamine andanother product of Example 1 for the4-ethoxy-1-ethyl-6-methyl-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylicacid ethyl ester:

1-Ethyl-4-ethylamino-6-methyl-1H-1,2,3-triazolo-[4,5-c]pyridine-7-carboxylicacid methyl ester.

4-Dimethylamino-1-ethyl-6-methyl-1H-1,2,3-triazolo-[4,5-c]pyridine-7-carboxylicacid and ethyl ester.

4-Diethylamino-1-methyl-1H-1,2,3-triazolo[4,5-c]-pyridine-7-carboxylicacid propyl ester.

1,6-diethyl-4-(methylethylamino)-1H-1,2,3-triazolo-[4,5-c]pyridine-7-carboxylicacid ethyl ester.

1-Methyl-4-phenylamino-1H-1,2,3-triazolo[4,5-c]-pyridine-7-carboxylicacid ethyl ester.

4-Amino-6-methyl-1-phenyl-1H-1,2,3-triazolo[4,5-c]-pyridine-7-carboxylicacid and ethyl ester.

4-Amino-6-methyl-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylic acid andethyl ester.

1-Benzyl-4-amino-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylic acidmethyl ester.

4-n-Butylamino-6-methyl-1-phenethyl-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylicacid ethyl ester.

EXAMPLE 41-Ethyl-6-methyl-4-[3-(dimethylamino)propyl]amino-1H-1,2,3-triazolo[4,5c]pyridine-7-carboxylicacid ethyl ester

(3-Dimethylamino)propylamine is substituted for the n-butylamine in theprocedure of Example 2 to obtain1-ethyl-6-methyl-4-[3-(dimethylamino)propyl]amino-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylicacid ethyl ester, yield 79%, m.p. 30°-34° (ethyl acetate).

The following additional products are obtained by the procedure ofExample 2 l by substituting a (lower alkylamino)lower alkylamine for then-butylamine and another product of Example 1 for thetriazolopyridinecarboxylic acid ester:

4-[(2-Diethylamino)ethylamino]-1H-1,2,3-triazolo-[4,5-c]pyridine-7-carboxylicacid ethyl ester.

4-(Dipropylaminomethylamino)-6-methyl-1-phenyl-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylicacid and ethyl ester.

EXAMPLE 51-Ethyl-4-hydrazino-6-methyl-1H-1,2,3-triazolo-[4,5-c]pyridine-7-carboxylicacid ethyl ester

By substituting hydrazine for the amine in the procedure of Example 2,1-ethyl-4-hydrazino-6-methyl-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylicacid ethyl ester is formed, yield 58%, m.p. 75°-78° (ethyl acetate).

The following additional products are obtained by the procedure ofExample 2 by substituting hydrazine, alkylhydrazine or phenylhydrazinefor the amine and another product of Example 1 for the triazolopyridineester:

4-(Methylhydrazino)-1-methyl-1H-1,2,3-triazolo[4,5-c]-pyridine-7-carboxylicacid n-butyl ester.

4-(Phenylhydrazino)-1-ethyl-6-methyl-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylicacid ethyl ester.

4-(Diethylhydrazino)-1,6-diethyl-1H-1,2,3-triazolo-[4,5-c]pyridine-7-carboxylicacid and ethyl ester.

4-Hydrazino-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylic acid ethylester.

4-(n-Propylhydrazino)-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylic acidethyl ester.

4-(Dimethylhydrazino)-1-ethyl-6-phenyl-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylicacid ethyl ester.

4-(Phenylhydrazino)-1-phenyl-1H-1,2,3-triazolo[4,5-c]-pyridine-7-carboxylicacid methyl ester.

4-(Methylhydrazino)-6-methyl-1H-1,2,3-triazolo-[4,5-c]pyridine-7-carboxylicacid propyl ester.

4-Hydrazino-1-ethyl-6-propyl-1H-1,2,3-triazolo-[4,5-c]pyridine-7-carboxylicacid and ethyl ester.

1-Benzyl-4-methylhydrazino-1H-1,2,3-triazolo[4,5-c]-pyridine-7-carboxylicacid methyl ester.

4-Hydrazino-6-methyl-1-phenethyl-1H-1,2,3-triazolo-[4,5-c]pyridine-7-carboxylicacid ethyl ester.

4-Hydrazino-6-methyl-1-phenyl-1H-1,2,3-triazolo[4,5-c]-pyridine-7-carboxylic acid methyl ester.

1-Benzyl-4-hydrazino-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylic acidmethyl ester.

4-Hydrazino-6-methyl-1H-1,2,3-triazolo[4,5-c]-pyridine-7-carboxylic acidpropyl ester.

EXAMPLE 61-Ethyl-6-methyl-4-[2-(1-methylethylidene)hydrazino]-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylicacid ethyl ester

2.6 g. of1-ethyl-4-hydrazino-6-methyl-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylicacid ethyl ester (0.01 mol.) are dissolved in 10 ml. of acetone. Onedrop of acetic acid is added and the mixture is allowed to standovernight. The excess acetone is distilled off in vacuo and the residueis recrystallized from petroleum ether to obtain1-ethyl-6-methyl-4-[2-(1-methylethylidene)hydrazino]-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylicacid ethyl ester in 95% yield, m.p. 68°-72°.

The following additional compounds are obtained by the procedure ofExample 6 by substituting another ketone for the acetone utilizing thesame or another hydrazine of Example 6.

1-Ethyl-6-methyl-4-[2-(1-ethylpropylidene)hydrazino]-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylicacid ethyl ester.

1-Ethyl-6-methyl-4-[2-(1-methylpropylidene)]hydrazino]-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylicacid ethyl ester.

1-Ethyl-6-methyl-4-[2-α-methylbenzylidene)]hydrazino]-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylicacid ethyl ester.

4-[2-(1-methylethylidene)hydrazino]-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylicacid ethyl ester.

4-[2-(1-methylethylidene)hydrazino]-1-ethyl-6-propyl-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylicacid ethyl ester.

4-[2-(1-methylethylidene)hydrazino]-6-methyl-1-phenethyl-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylicacid ethyl ester.

4-[2-(1-methylethylidene)hydrazino]-6-methyl-1-phenyl-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylicacid methyl ester.

1-Benzyl-4-[2-(1-methylpropylidene)hydrazino]-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylicacid methyl ester.

4-[2-(α-methylbenzylidene)hydrazino]-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylicacid ethyl ester.

4-[2-(1-methylethylidene)hydrazino]-6-methyl-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylicacid propyl ester.

EXAMPLE 71-Ethyl-6-methyl-4-[(N-methyl)piperazino]-1H-1,2,3-triazolo-[4,5-c]pyridine-7-carboxylicacid ethyl ester

a.4-Chloro-2-methyl-5-nitro-6-[(N-methyl)piperazino]pyridine-3-carboxylicacid ethyl ester

By substituting (N-methyl)piperazine for the ethylamine in the procedureof Example 1b,4-chloro-2-methyl-5-nitro-6-[(N-methyl)piperazino)pyridine-3-carboxylicacid ethyl ester is formed, yield 64%, m.p. 62°-64° (methanol).

b.4-Ethylamino-2-methyl-5-nitro-6-[(N-methyl)piperazino]-pyridine-3-carboxylicacid ethyl ester

32.7 g. of4-chloro-2-methyl-5-nitro-6-[(N-methyl)-piperazino]pyridine-3-carboxylicacid ethyl ester (0.1 mol.) and 12 g. of triethylamine are treated withstirring in 100 ml. of alcohol at reflux temperature with 6 g. ofethylamie for 1 hour. After this time, the solution is evaporated anddissolved in 100 ml. of ether. The precipitated triethylaminehydrochloride is filtered off and the filtrate cooled to -30°.4-Ethylamino-2-methyl-5-nitro-6-[(N-methyl)piperazino]-pyridine-3-carboxylicacid ethyl ester precipitates, yield 73%, m.p. 59°-61° (methanol).

c. 5-Amino-4-ethylamino-2-methyl-6-[(N-methyl)piperazino]-pyridine-3-carboxylicacid ethyl ester

By substituting4-ethylamino-2-methyl-5-nitro-6-[(N-methyl)piperazino]pyridine-3-carboxylicacid ethyl ester in the procedure of Example 1d,5-amino-4-ethylamino-2-methyl-6-[(N-methyl)piperazino]pyridine-3-carboxylicacid ethyl ester is formed, yield 94%, b.p. 210°-220°/₀.01.

d.1-Ethyl-6-methyl-4-[(N-methyl)piperazino]pyridine-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylicacid ethyl ester

By substituting5-amino-4-ethylamino-2-methyl-6-[(N-methyl)piperazino]pyridine-3-carboxylicacid ethyl ester in the procedure of Example 1e,1-ethyl-6-methyl-4-[(N-methyl)-piperazino]-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylicacid ethyl ester is produced, yield 83%, m.p. 63°-65° (petroleum ether).

EXAMPLE 81-Ethyl-6-methyl-4-piperidino-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylicacid ethyl ester

By substituting piperidine for (N-methyl)piperazine in Example 7a, andthis compound processed according to the procedures of Example 7b, c andd,1-ethyl-6-methyl-4-piperidino-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylicacid ethyl ester is formed, m.p. 45°-47° (petroleum ether).

The following additional products are obtained when piperazine,pyrrolidine, piperidine, pyrazoline, pyrimidine, pyridazine or4-(hydroxyethyl)piperazine is substituted for the ethylamine in theprocedure of Example 1b:

1-Ethyl-6-methyl-4-piperizino-1H-1,2,3-triazolo-[4,5-c]pyridine-7-carboxylicacid ethyl ester.

1-Ethyl-6-methyl-4-pyrrolidino-1H-1,2,3-triazolo-[4,5-c]pyridine-7-carboxylicacid ethyl ester.

1-Ethyl-6-methyl-4-piperidino-1H-1,2,3-triazolo-[4,5-c]pyridine-7-carboxylicacid ethyl ester.

1-Ethyl-6-methyl-4-(4-ethylpiperidino)-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylicacid ethyl ester.

1-Ethyl-6-methyl-4-pyrazolino-1H-1,2,3-triazolo-[4,5-c]pyridine-7-carboxylicacid ethyl ester.

1-Ethyl-6-methyl-4-pyrimidino-1-H-1,2,3-triazolo-[4,5-c]pyridine-7-carboxylicacid ethyl ester.

1-Ethyl-6-methyl-4-pyridazino-1H-1,2,3-triazolo-[4,5-c]pyridine-7-carboxylicacid ethyl ester.

1-Ethyl-6-methyl-4-[4-(2-hydroxyethyl)piperazino]-1H-1,2,3-triazolo[4,5-c]pyridine-7-carboxylicacid and ethyl ester.

What is claimed is:
 1. A compound of the formula ##SPC13##wherein R ishydrogen or lower alkyl; R₁ is hydrogen, lower alkyl, phenyl, benzyl orphenethyl; and R₃, R₆ and R₇ each is hydrogen, lower alkyl or phenyl. 2.A compound as in claim 1 wherein R, R₁, R₃, R₆ and R₇ each is hydrogenor lower alkyl.
 3. A compound as in claim 1 wherein R, R₁ and R₃ each islower alkyl and R₆ and and R₇ each is hydrogen or lower alkyl.
 4. Acompound as in claim 3 wherein R and R₁ each is ethyl; R₃ is methyl; andR₆ and R₇ each is hydrogen.